$18.$ Assume that a noncallable $10-$year T$-$bond has a $12\%$ annual coupon, while a $15-$year noncallable T$-$bond has an $8\%$ annual coupon. Assume also that the yield curve is flat, and all Treasury securities have a $10\%$ vield to maturity. Which of the following statements is CORRECT?a$.$ The $10-$year bond would sell at a premium, while the $15-$year bond would sell at par.b$.$ If interest rates decline, the prices of both bonds would increase, but the $10-$year bond would have a larger percentage increase in price.c$.$ The $10-$year bond would sell at a discount, while the $15-$year bond would sell at a premium.d$.$ If interest rates decline, the prices of both bonds would increase, but the $15-$vear bond would have a larger percentage increase in price.e$.$ If the yield to maturity on both bonds remains at $10\%$ over the next year, the price of the $10-$year bond would increase, but the price of the $15-$year bond would fall.